Laterally expandable security grilles of the type having a series of parallel uprights interlinked by means of laterally inclined link members are often made with each upright being composed of two parallel, spaced metal tubes, fixed together at spaced positions up to the height thereof. The resultant space between the two tubes receives the lateral link members passing therethrough. The link members are pivotally attached, either at one of their ends, or in the middle thereof, to one composite upright. Their free ends are held captive relative to an adjacent composite upright by means of a transverse axle or stud member passing through the link members and extending into a slot in each of the inwardly directed faces of the two tubes defining the composite upright.
The slot serves both to hold the axle or stud member captive and to guide it for longitudinal movement along the slot as the uprights are moved towards or away from each other.
Security grilles of this type at the lower end of the market, may have slots simply cut in the metal which co-operate with the axle or stud member. More sophisticated security grilles have a plastic insert for receiving the axle or stud member. In such a case each insert is installed in a hole punched in the wall of the metal tube, and the insert has a surrounding flange adjacent the face of the metal tube. The slot defined by the insert defines surfaces against which the axle or stud can slide smoothly. The insert is open at its inner end.
The type of insert described above, which is generally made of a suitable injection moulded plastics material, such as polypropylene, operates generally effectively, apart from two disadvantages.
The first disadvantage is that, the slot being open at its inner end, allows the ingress of moisture and other corrosive airborne materials. The second disadvantage is that the surrounding flange is somewhat square in cross-section and can interfere with the rotation of the link members about their pivots as the composite uprights are moved towards each other to open the security grille.
It is the object of the present invention to provide inserts; composite uprights embodying the same, and security grilles including such composite uprights, wherein effective sealing of an insert is possible, and also, interference of movement of the link members by the flange of the insert is decreased or eliminated entirely.